When an automatic transmission (A/T) vehicle generating driving force by an engine has a traveling position (a forward position or a reverse position) selected, it generates a force to propel a vehicle to creep at a slow speed even if the accelerator pedal is not operated. An electric vehicle (EV) generating driving force by an electric motor and a hybrid vehicle (HV) generating driving force by both an engine and an electric motor generate a creep force by a torque that the electric motor generates. For such vehicles generating a creep force by an electric motor a technique improving driveability and reducing wasteful electric power consumption is disclosed in Japanese Patent Laying-open No. 2006-50811.
Japanese Patent Laying-open No. 2006-50811 discloses an electric vehicle generating a creep torque by a driving force that an electric motor generates when a predetermined condition is established. The electric vehicle includes: a detection unit detecting a driver's brake pedal operation; a vehicular speed detection unit detecting vehicular speed; a first creep torque setting unit setting a creep torque command value in accordance with vehicular speed, as based on a predetermined reference characteristic line, when a creep torque is generated; and a creep torque cutting unit setting an upper limit value for a creep torque in accordance with an amount by which the brake pedal is operated when a creep torque is generated and the driver presses the brake pedal. The creep torque cutting unit includes: a plurality of units setting an upper limit value for a creep torque, as based respectively on a predetermined plurality of upper limit value setting characteristic lines setting an upper limit value for a creep torque in accordance with an amount by which the brake pedal is operated; a unit selecting in accordance with the vehicles condition one of the plurality of units setting an upper limit value for a creep torque; and a second creep torque setting unit setting an upper limit value for a torque that is set by the selected unit setting an upper limit value for a creep torque, as a new creep torque command value if a creep torque command value set by the first creep torque setting unit is larger than the upper limit value for a torque that is set by the selected unit setting an upper limit value for a creep torque.
According to Japanese Patent Laying-open No. 2006-50811, when the electric vehicle generates a creep torque and also has the brake pedal pressed, an upper limit value can be set for the creep torque to cut the creep torque, and a plurality of characteristic lines setting an upper limit value for a creep torque can selectively be used in accordance with the vehicle's condition to set an upper limit value. Thus when the brake pedal is pressed an appropriate creep torque can be generated in accordance with the vehicles condition. The vehicle can thus be improved in driveability and reduce wasteful electric power consumption.
In recent years a vehicle is known that reduces a burden on a driver operating a brake in a traffic jam and the like. More specifically, when the vehicle is stopped in a forward position and in that condition once the vehicle has the brake pedal operated to a degree (e.g., in an amount) larger than a predetermined threshold value, then thereafter even if the brake pedal is not operated the braking force applied when the vehicle is stopped is maintained (i.e., brake hold control is exerted).
The electric vehicle disclosed in Japanese Patent Laying-open No. 2006-50811 cuts a creep torque in accordance with an amount by which the brake pedal is operated. However, the document is silent on a case where the brake hold control is exerted (i.e., a braking force is maintained while the brake pedal is not operated.)